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(#) Likely cut & paste mistakes

!!! WARNING: Likely cut & paste mistakes
   This is a warning.

Id
:   `CutPasteId`
Summary
:   Likely cut & paste mistakes
Severity
:   Warning
Category
:   Correctness
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   Initial
Affects
:   Kotlin and Java files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/CutPasteDetector.java)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/CutPasteDetectorTest.java)
Copyright Year
:   2012

This lint check looks for cases where you have cut & pasted calls to
`findViewById` but have forgotten to update the R.id field. It's
possible that your code is simply (redundantly) looking up the field
repeatedly, but lint cannot distinguish that from a case where you for
example want to initialize fields `prev` and `next` and you cut & pasted
`findViewById(R.id.prev)` and forgot to update the second initialization
to `R.id.next`.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
src/test/pkg/PasteError.java:10:Warning: The id R.id.previous has
already been looked up in this method; possible cut & paste error?
[CutPasteId]
    next = (Button) findViewById(R.id.previous); // TYPO, meant R.id.next
                    ---------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here are the relevant source files:

`src/test/pkg/PasteError.java`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers
package test.pkg;
import android.app.Activity;
import android.widget.Button;

public class PasteError extends Activity {
    private Button next;
    private Button previous;
    protected void onCreate() {
        previous = (Button) findViewById(R.id.previous);
        next = (Button) findViewById(R.id.previous); // TYPO, meant R.id.next
    }
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

`test.pkg`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text linenumbers
@id/next
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/CutPasteDetectorTest.java)
for the unit tests for this check to see additional scenarios.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("CutPasteId")
  fun method() {
     findViewById(...)
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("CutPasteId")
  void method() {
     findViewById(...);
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection CutPasteId
  problematicStatement()
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="CutPasteId" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'CutPasteId'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore CutPasteId ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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